feat: public shopping list links can allow editing

Owner opts in per-list via a new "Allow editing" toggle next to the
existing public-link switch. Anonymous writes are scoped to that one
list only — the link id is the sole credential, enforced in
getShoppingListAccess and the item routes (no session required there
now), with an IP rate limit on genuinely anonymous requests. Turning
off the public link also revokes editing.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/web/lib/shopping-list-notify.ts

@@ -44,7 +44,10 @@ async function getOtherRecipients(listId: string, actorId: string) {
 export async function notifyShoppingListMembers(
   listId: string,
   actorId: string,
-  actorName: string,
+  // null actorName = an anonymous edit via a public-editable share link — no
+  // per-visitor identity exists, so this is rendered as a localized generic
+  // label (per recipient's own locale) rather than a real name.
+  actorName: string | null,
   event: { type: "checked" | "itemsAdded"; itemName?: string; count?: number; listName: string }
 ): Promise<void> {
   const recipients = await getOtherRecipients(listId, actorId);
@@ -57,16 +60,17 @@ export async function notifyShoppingListMembers(
       if (!(await isNotificationCategoryEnabled(recipient.id, "shoppingList"))) return;
 
       const messages = getMessages(recipient.locale);
+      const displayName = actorName ?? messages.publicShoppingList.anonymousEditor;
       const title = messages.notifications.pushTitle.shoppingListUpdate;
       const body =
         event.type === "checked"
           ? formatMessage(messages.notifications.detail.shoppingListChecked, {
-              name: actorName,
+              name: displayName,
               item: event.itemName ?? "",
               list: event.listName,
             })
           : formatMessage(messages.notifications.detail.shoppingListItemsAdded, {
-              name: actorName,
+              name: displayName,
               countLabel: itemsCountLabel(event.count ?? 1, recipient.locale),
               list: event.listName,
             });